Dealing with Waifu's S.O. in their stories

[Mercyknight]

there is a simple answer. what is cannon, is cannon for that universe, your own version is an alternate reality and thus not subject to the rules of the cannon universe. in the cannon one the royal sisters have no other siblings, and we never see their parents. in my version I have met them, and the girls adopted me as a sibling.

also their parents are quite nice, and their mother knows her way around potions